[libsoup/fix-error-string-is-not-a-literal-string: 9/9] Fix Clang compilation error 'format string is not a string literal'

[Diego Pino <dpino src gnome org>]

commit af6cf7913827e8e2d360d69e95c4dda106c03d80
Author: Diego Pino Garcia <dpino igalia com>
Date:   Wed May 19 16:30:25 2021 +0800

    Fix Clang compilation error 'format string is not a string literal'

 libsoup/http2/soup-client-message-io-http2.c | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/libsoup/http2/soup-client-message-io-http2.c b/libsoup/http2/soup-client-message-io-http2.c
index 0b09ee14..12eb2e16 100644
--- a/libsoup/http2/soup-client-message-io-http2.c
+++ b/libsoup/http2/soup-client-message-io-http2.c
@@ -186,6 +186,7 @@ state_to_string (SoupHTTP2IOState state)
         }
 }
 
+G_GNUC_PRINTF(3, 0)
 static void
 h2_debug (SoupClientMessageIOHTTP2   *io,
           SoupHTTP2MessageData       *data,
@@ -1325,6 +1326,7 @@ static const SoupClientMessageIOFuncs io_funcs = {
         soup_client_message_io_http2_is_reusable
 };
 
+G_GNUC_PRINTF(1, 0)
 static void
 debug_nghttp2 (const char *format,
                va_list     args)